Piezo-quartz

Fig. 12.7. Interaction of mercury vapour with thin gold films coated by self-assembled monolayer of 1-hexadecanethiol (a) comparison of the kinetics of resistive response for bare (open symbols) and coated (filled symbols) gold films on exposure to 10 ng/1 mercury vapour (b) influence of different mercury vapour concentrations on the resistance of coated electrodes (c) kinetics of changes of the resonance frequency of a 1-hexadecanethiol-coated piezo-quartz due to exposure to 8.3 ng/1 of mercury vapour [25].

Measurements of sound velocity at ultrasonic frequencies are usually made by an acoustic interferometer. An example of this apparatus11 is shown in Fig. 2. An optically flat piezo-quartz crystal is set into oscillation by an appropriate electrical circuit, which is coupled to an accurate means of measuring electrical power consumption. A reflector, consisting of a bronze piston with an optically flat head parallel to the oscillating face of the quartz, is moved slowly towards or away from the quartz by a micrometer screw. The electrical power consumption shows successive fluctuations as the distance between quartz and reflector varies between positions of resonance and non-resonance of the gas column. Measurement of the distance between resonance positions gives a value for A/2, and if /... 

A complete gas pressure curve can only be plotted with the aid of piezo-quartz or other pressure recorder in conjunction with an oscillograph (-> Ballistic Bomb). 

The determination of the thrust of a rocket motor involves recording the time diagram of the force (tons, kp, or newtons) during combustion. The force is allowed to act on a support, with a pick-up element thrust cell interposed between them. The measurement is carried out by the aid of a strain gauge element (variation of resistance with pressure) or of a piezo-quartz element, and the results are recorded on an oscillograph connected in a compensation circuit. Modern measuring and computation techniques yield the total thrust time (impulse) immediately. 

Terent yev and Klabimovskii hydrogenated the ethyl-(2-phenylciimamate) (Scheme 2.6.) in decalin solution at 135°C on a Ni-r/-piezo-quartz catalyst and received a product with Od = -0.09° 0.007°. On Ni-/-quartz the product had an optical rotation of +0.04°. 

Hence the respective flow fields can be exactly calculated from the Navier Stokes equations, at least for low frequencies, i. e. laminar flows. This is not the case for linear oscillations at either low frequencies, i. e. the linear spring in gas system [3.1], or high frequencies, namely piezo-quartz systems bearing sorbent samples [5.10] or oscillating rod systems (SETARAM). Also at high frequencies the state of the sorbate phase may become transient , i. e. deviate considerably from a thermodynamic equilibrium state. 

Piezoelectric energy is a form of electric energy produced by certain solid materials when they are deformed. (The word piezo has its roots in the Greek word piezein meaning to press. ) Discovery of the piezoelectric effect is credited to Pierre and Jacques Curie who observed in 1880 that certain quartz crystals produced electricity when put under pressure. 

Piezo-electric hygrometry employing a quartz crystal with a hygroscopic coating in which moisture is alternately absorbed from a wet-gas and desorbed in a dry-gas stream the dynamics is a function of the gas humidity. 

Alpha-quartz has many useful properties which lead to its wide use in industry as a glass, ceramic and molecular sieve. However, undoubtedly its most technically important use occurs by virtue of its piezo-electric properties, which allow it to be used as a frequency regulating device in satellites, computers, and the ubiquitous quartz-watch . Unfortunately, it has been found that quartz crystals are susceptible to damage by radiation, and that this is associated with the presence of defects in the crystal lattice. These defects, particularly aluminum and hydrogen, are grown into the crystal and so far have proved impossible to remove. This problem has been the cause of intensive research, which has led to some information on the possible types of defects involved, but has failed to produce details of their geometries, and the way in which they interact. 

Curie, J. (1889). Quartz piezo-electrique. Annales de Chimie et de Physique, 17, 392-401. 

The piezo-electric effect of deformations of quartz under alternating current (at a frequency in the order of 10 MHz) is used by coating the crystal with a selectively binding substance, e. g. an antibody. When exposed to the antigen, an antibody-antigen complex will be formed on the surface and shift the resonance frequency of the crystal proportionally to the mass increment which is, in turn, proportional to the antigen concentration. A similar approach is used with surface acoustic wave detectors [142] or with the surface plasmon resonance technology (BIAcore, Pharmacia). 

Sauerbrey [7] in 1959 related the change in resonance frequency of a piezo-electric quartz crystal with the mass deposited onto or removed from the crystal surface. This approach has been used to perform micro-gravimetric measurements in the gas phase like metal evaporation. For (Afo) the Sauerbrey equation states that ... 

In the case of viscoelastic loaded QCM two approaches have been followed one methodology is to treat the device as an acoustic transmission line with one driven piezo-electric quartz layer and one or more surface mechanical load (TLM) [50, 51]. A simpler approach is to use a lumped-element model (LEM) that represents mechanical inter-actions by their equivalent electrical BVD circuit components [52, 53]. 

Fig. 2. Measuring set-up (A) photograph of the piezoelectric device and flow system, the inset shows the cell holding the quartz sensor (B) sample QCM sensor with 10 MHz base frequency (as used throughout the described experiments) (C) cross-section through the piezo-cell showing the two rubber O-rings holding the quartz plate, only one side of the sensor is in contact with the fluid (D) cross-section of the cell used for combined piezoelectric and amperometric measurements, the lid also hold a titanium wire electrode and the Ag/AgCI reference electrode.

Any type of acoustic transducer, such as quartz crystal microbalance (QCM) or surface acoustic wave device (SAW), is fundamentally based on the piezoelectric effect. This was first described in 1880 by Jacques and Pierre Curie as a property of crystalline materials that do not have an inversion centre. When such a material is subjected to physical stress, a measurable voltage occurs on the crystal surfaces. Naturally, the opposite effect can also be observed, i.e. applying an electrical charge on a piezoelectric material leads to mechanical distortion, the so-called inverse piezo effect. These phenomena can be used to transfrom an electrical signal to a mechanical one and back, which actually happens in QCM and SAW. Different materials are ap-pHed for device fabrication, such as quartz, Hthium tantalate, lithium titanate... 

The components of a TS system are shown in Figure 11.39 (130). A resonance stethoscope is used to transmit crystalline vibrations in the sample to the audio frequency range where they are converted to electrical signals by use of a piezo-electric crystal. The stethoscope is constructed of quartz, which, because of its high Q value, operates mechanically both as a tuned pick-up sensor and as a self-exciting resonator. The unit incorporates a sample-holder head shaped as an acoustic transformer and fitted with a transmitter rod that mechanically matches the piezo-electric cell fixed on a heavy recoil... 

Certain materials produce electric charges on their surfaces as a consequence of applying mechanical stress. The induced charges are proportional to the mechanical stress. This is called the direct piezoelectric effect and was discovered in quartz by Piere and Jacques Curie in 1880. Materials showing this phenomenon also conversely have a geometric strain proportional to an applied electric field. This is the converse piezoelectric effect. The root of the word piezo means pressure hence the original meaning of the word piezoelectricity implied pressure electricity . 

Thus there are many piezo devices using these phenomena. Microphone membranes (PE), loud speakers (RPE), sonar (historically the first application RPE), piezoresistors (PR) for pressure measurements, cigarette lighters (PE), and quartz watches (RPE) are examples. 

Mason WP (ed) (1964) Physical acoustics. Academic, New York, NY Nelson DF (1979) Electric, optic and acoustic interactions in dielectrics. Wiley, New York, NY Thomson W (Lord Kelvin) (1878) On the piezoelectric property of quartz. Phil Mag 5 4 Tichy J, Gautschi G (1980) Piezoelektrische Messtechnik. Springer, Heidelberg Toledano P, Dmitriev V (1996) Reconstructive phase transitions. World Scientific, Singapore Valasek J (1920) Piezoelectric and allied phenomena in Rochelle salt. Phys Rev 15 537-538 Valasek J (1921) Piezoelectricity and allied phenomena in Rochelle salt. Phys Rev 17 475-481 Valasek J (1922) Piezo-electric activity of Rochelle salt under various conditions. Phys Rev 19 478 Valasek J (1924) Dielectric anomalies in Rochelle salt crystals. Phys Rev 24 560 Voigt W (1890) General theory of the piezo- and pyroelectric properties of crystals. Abh Gott 36 1-99... 

For the structure of tensor components of the nonlinear material coefficient see Table 7.3. Piezo-optical, elasto-optical and electro-elastic coefficients for a-quartz are listed in Table 7.4. 

Certain crystals, such as quartz, feature a physical relationship between mechanical force and electric charge. When the crystal lattice ions are elastically shifted relative to one another due to an external force, an electric polarization can be detected by means of metallic electrodes on the surface. This so-called piezoelectric effect was first scientifically explained by the brothers Jacques and Pierre Curie in 1880 and forms the basis for piezo sensors (see Sect. 7.3). The effect is reversible and is then called reciprocal or inverse piezoelectric effect. If, for instance, an electric voltage is applied to a disc shaped piezo crystal, the thickness of the crystal changes due to the reciprocal piezoelectric effect. It is this property that is made use of in actuators. 

The phenomenon which is described by the third degree tensor d.ji is called piezo-electric effect and it is manifested, for instance, by many quartz crystals, tourmaline with the following formula (Na,Ca) (Al,Fe,Li,Mg)3Alg(B03)3(Sig0j3) and others. 

In 1880, Pierre Curie and his brother Jacques made the first observation of the piezo-dectric effeU. What they found was that some crystals, e.g. quartz, are deformed mechanically when an electrical voltage is applied to them. An AC electric potential might thus cause vibration. This made possible the generation and reception of ultrasound (a sound with such a high frequency, more than 15 000 Hz = 15 kHz, so that the human ear cannot hear it). For technical and medical uses of ultrasound, still... 

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